The price of saving the world's frogs, toads and salamanders from oblivion will top $400m (£220m) over five years.

This is the estimated cost of a global action plan drawn up during an expert summit in Washington DC, and backed by the UN's biodiversity agency IUCN.

The money would pay for the protection of habitats, for disease prevention and captive-breeding projects, and for the ability to respond to emergencies.

About a third of all amphibian species are at a high risk of extinction.

"Many species have already become extinct through habitat loss," Rohan Pethiyagoda, deputy chair of IUCN's species survival commission, told the BBC News website.

"The extent of these declines and extinctions is without precedent in any class of animals over the last few millennia."

Plotting the decline

According to the Global Amphibian Assessment, a vast and authoritative study which reported its findings last year, almost a third of the 5,743 known species are at risk of extinction; up to 122 have disappeared within the last 25 years.

The action plan emerging from this meeting lists six major reasons behind the decline:

habitat loss and degradation

climate change

chemical contamination

infectious disease, notably the fungal infection chytridiomycosis

invasive species

over-harvesting

Over the three days, working groups drawn from a wide range of scientific institutions and conservation organisations have established budgets for tackling each of these issues; the overall total comes to US$404m (£223m).

Chytridiomycosis, a fungal disease which emerged in the 1970s, occupied much of the delegates' attention.

It has devastated populations, particularly in south and central America, but is also firmly established in Australia, Africa and Europe.

WHAT ARE AMPHIBIANS?

Group includes frogs, toads, salamanders and caecilians

First true amphibians evolved about 250m years ago

Adapted to many different aquatic and terrestrial habitats

Present today on every continent except Antarctica

Undergo metamorphosis, from larvae to adults

So widespread and so devastating is Batrachochytrium dendrobatidis, the fungus responsible, that one of the main recommendations emerging in the action plan is that extensive captive-breeding programmes should be established for amphibians at particular risk.

The plan envisages that, ultimately, around 1,000 species could be preserved in this way, with specialist facilities established on every continent.

But not all delegates believe this to be an effective approach.

"Many species can't be bred in captivity," Cynthia Carey, from the University of Colorado, US, told the BBC News website, "and with 99% of the species they're looking at, we just don't know how to do it.

"You can give them the right habitat and food, but they may need specific light or heat or moisture or group size, otherwise the female won't ovulate - and it can take years to study that."

The action plan sees captive breeding as a bridge to a better era when chytridiomycosis can be beaten and the amphibians returned to the wild.

"We've been running a captive-breeding programme with the boreal toad (Bufo boreas) since 1995," said Professor Carey.

"We've tried re-introducing them to the wild seven or eight times, but every time they die within a couple of years; if you don't get rid of the fungus, all you're doing is providing it with lunch."

Developing resistance

Part of the US$404m would be spent on investigating ways of dealing with Batrachochytrium. Ideas include researching why some species are immune, which could lead to drugs or even a vaccine, though that is considered to be a long way off.

More than 1,800 amphibian species are in difficulties (Image: Forrest Brem/Roberto Brenes)

Another idea is developing fungal resistance in captive populations through cross-breeding before returning them to the wild.

"But we also need to identify critical habitats, protect them and then enforce protection," said Rohan Pethiyagoda, who runs the Wildlife Heritage Trust in Sri Lanka.

"Where I come from, 95% of the original habitat has already disappeared; and sometimes the patches left are less than one square kilometre in size."

Other sums would go towards combating over-harvesting - the unsustainable use of amphibians for food, medicine and the pet trade - and to establishing rapid-response teams that could travel to a site when a particular population collapses.

Early warning?

All sources will be explored for funding. At the meeting, two grants amounting to a total of US$700,000 were announced, and there were indications that the powerful Global Environment Facility may be willing to invest.

Many delegates emphasised the importance of putting amphibian decline in the context of broader environmental change and its impact on human societies.

"We all know that amphibian decline is just the first manifestation of synergies between different factors," said Tom Lovejoy, the president of the Heinz Center for Science, Economics and the Environment in Washington.

"We're living in this global soup of chemicals; there's climate change, the oceans are already a tenth of a percent more acid than they were.

"So, by finding ways to manage the first manifestation of these negative synergies, we'll be better able to deal with other manifestations what will occur in the future."

But others were less optimistic that US$404m - even presuming that it is forthcoming - can make much a difference.

"I would be optimistic if people started doing something about the underlying issues such as climate change and pollution," said Professor Tim Halliday, international director of the Declining Amphibians Task Force.